1. Technical Field
The present application relates to an in-vehicle electronic device, and more particularly to the in-vehicle electronic device housing a multilayer circuit board mounted with electronic components in a housing.
2. Background Art
The in-vehicle electronic device hermetically sandwiches and houses the circuit board in the housing constituted by a flat or deep bottom base member mounted and fixed to a vehicle body, and a flat or deep bottom cover member fastened and fixed to the base member. A connector housing is attached to the circuit board, an end surface of the connector housing is exposed from a side surface of the housing, and a connector is removably attached thereto so that a power supply line and an input/output signal line are connected to the connector. In this type of in-vehicle electronic device, electromagnetic interference is a major problem, and for example, in Patent Literature 1, in order to prevent an LSI and the like of the in-vehicle electronic device from malfunctioning due to static electricity or noise, a ground pattern is provided in an electronic substrate sandwiched by a metal base member and a cover member, the ground pattern is grounded to a conductive portion of the vehicle body via a connection terminal of the connector housing, and a protection pattern connected with a capacitor is disposed on an outer peripheral portion of the ground pattern, so that static electricity and noise are easily conducted to the protection pattern. Patent Literature 1 further proposes that a cut portion is provided in a portion facing an integrated circuit element (LSI) of the protection pattern, and the protection pattern is configured not to operate as a loop antenna, so that malfunction or breakage of the integrated circuit element can be prevented.
Further, the Patent Literature 1 discloses that the protection pattern is electrically conductively connected to the base member or AC-connected via a high dielectric body and DC-disconnected, to be a capacitor. That is, when the high dielectric body is used, the protection pattern is AC-connected to the base member via the high dielectric body, and the base member is attached to conduct to the vehicle body. Furthermore, the Patent Literature 1 discloses that the protection pattern is provided as an island-like protection pattern and brought into conductive contact with the base member.